Invertebrate functional responses to hydro­morpho­logical degradation in Mediterranean Croatian rivers

Abstract

Hydromorphological alterations are among the most widespread anthropogenic pressures in rivers andstreams. They comprise channelization, damming, water abstraction etc. resulting in habitats alteration and subsequentchanges in aquatic community composition. Aim of this study was to test to what extent hydromorphologicalalterations influence aquatic macroinvertebrates as one of the best bioindicators to anthropogenic pressures. Our researchtook place in the Mediterranean part of Croatia. We sampled 40 sites which include perennial rivers varyingin catchment size and altitude with similar environmental conditions along river reaches. Large rivers were omittedfrom this research because of their different functional group representation to the rivers covered used in this study.We used the functional approach to hydromorphological alteration by testing the following traits: reproductionstrategy, functional feeding group and microhabitat (substrate type) preference. From the feeding standpoint shredderswere the most affected group by hydrological alteration. Moreover, taxa confined to a specific relatively lesscommon habitat e.g. phytal, pelal and lithal were the most negatively affected by morphological degradation due,mostly, to it leading to a homogenization of the substrate. Finally, the smaller and faster reproductive taxa weremore resilient to hydromorphological degradation. We found that the functional approach to bioassessment complementsthe common biocenotical approach, at the same time it may provide sound ecological knowledge.